The present invention generally relates to the optimization of the performance of a storage system.
As a technology for distributing the load of a storage device, the technology disclosed in Japanese Application Laid Open Nos. H7-56691 and 2006-53601, for example, are known. Japanese Application Laid Open No. H7-56691 discloses a load distribution technology for a plurality of disk devices that constitute a striping disk. Japanese Application Laid Open No. 2006-53601 discloses a load distribution technology of a logical storage device (logical volume).
Normally, a storage system performs storage control, which utilizes RAID (Redundant Array of Independent (or Inexpensive) Disks) technology. More specifically, for example, a storage system comprises a RAID group that is constituted by two or more physical storage devices (also known as a ‘parity group’ or an ‘array group’) and storage control that is adapted to the RAID level of the RAID group is carried out.
RAID levels that are generally adopted include RAID levels which, even when a fault occurs in one of the two or more physical storage devices constituting the RAID group, allow data elements stored in a physical storage device in which a fault occurs to be recovered (‘recoverable’ RAID level hereinbelow) and, more specifically, RAID levels other than RAID0 (RAID1, RAID5, or RAID6, for example).
The physical storage device comprises a plurality of physical storage areas. The loads of two or more physical storage devices that constitute the same RAID group are sometimes subject to scattering due to the access pattern. Hence, the distribution of the load of the physical storage device and, more specifically, the re-arrangement of the data elements in physical storage area units is thought to be desirable.
Further, each time such load distribution is performed, redundancy must be maintained in cases where a recoverable RAID level is adopted. However, according to Japanese Application Laid Open No. H7-56691, because of the load distribution of a plurality of disk devices constituting a striping disk, in other words, the load distribution in cases where the RAID level is RAID0, load distribution that considers redundancy is not carried out. In addition, according to the technology disclosed in Japanese Application Laid Open No. 2006-53601, the load of the logical storage devices (logical volumes) rather than the load of the physical storage devices is distributed.